I have always considered my Model S a luxury and I think scrimping on a luxury is self defeating, consequently when I ordered my Model S I bought a fully loaded P85. There were two features that many of us wanted and were not then available for purchase:

1) Power Folding Mirrors
2) Parking Assist

My Model S recently went to the Bellevue Service center for its 12 month service and the addition of the new Battery Shield. I was given a loaner model recently produced which had both of these two features installed. My techno-lust was instantly aroused and I asked if these items could be retro-fit. The answer was yes, for a price ...

It turns out the power mirrors were only about $2400. Since I have to manually fold in my driver's side mirror every day when I park in my garage, I thought this was worth it. The parking assist was a much more expensive matter. The service center will not drill your existing bumpers (6-8 holes?) for the sensors. You have to buy new pre-drilled bumpers from the factory. AND since I had already replaced a bumper, I knew that bumpers come from the factory UNPAINTED. This means the service center needs to send out to a sub contractor for the painting. AND since I had paint protection film, it meant that the new bumpers would have the paint protection film added after the paint by a different sub contractor. I swallowed hard and said yes to another $6000 for the parking assist retrofit. After sales tax (9.4% in Bellevue, WA) the total bill was just short of $10K.